Synchronizing mechanisms for power transmissions

ABSTRACT

A device for synchronizing the speed of two torque transmitting members of a vehicle gearbox has a cone clutch engagable by actuating pins which pass through clearance holes in an axially slidable clutching member. Each pin has a shoulder which balks axial movement of the clutching member when the axes of the pins are moved out of alignment with the axes of the holes in said member when torque is transmitted by the cone clutch. The clutching member carries springs which centralize the pins axially of said member to ensure movement of the pins in unison with said member and to reduce wear of the pins and the clearance holes.

United States Patent 1151 3,695,403 Eastwood [451 Oct. 3, I972 154]SYNCHRONIZING MECHANISMS FOR 2,256,308 9/1941 Bixby et a1. 192/53 EPOWER TRANSMISSIONS FOREIGN PATENTS OR APPLICATIONS [72] Inventor:Thomas Eastwood, Meltham, En-

gland 1,098,083 3/1955 France ..192/53 G [73] Assignee: David BrownTractors Limited P i E i -All D, H m n [22] Filed: March 2 1970Attorney-Norris & Bateman 211 App1.No.: 15,579 57 ABSTRACT A device forsynchronizing the speed of two torque [30] Foreign Application PriorityData transmitting members of a vehicle gearbox has a cone March 6 1969Great Britain 1 1 914/69 clutch engagable by actuating pins which passthrough clearance holes in an axially slidable clutching member. Eachpin has a shoulder which balks axial ((51. ..192/53 movement of theclutching member when the axes of the p are moved out of alignment withthe axes of [58] Field of Search ..192/53 E, 53 F, 53 G the holes inSaid member when torque is transmitted by the cone clutch. The clutchingmember carries [56] References Cited springs which centralize the pinsaxially of said UNITED STATES PATENTS member to ensure movement of thepins in unison 3 365 039 H1968 St t t I 192/53 F with said member and toreduce wear of the pins and O te a. th 1 Ce holes. 3,419,120 12/1968 sum..192/53 F e 6 3,419,121 12/1968 Stott ..192/53 F 8 Claims, 4 DrawingFigures PATENTED "E 3 I973 SHEET 1 [IF 3 INVENTOR THOMAS EASTWOOD BY WW1655;)

NORRIS & BATEMAN PATENTEUUCT 3 m2 SHEET 2 BF 3 INVENTOR THOMAS EASTWOODNORRIS & BATEMAN PATENTEDHBT3 I912 3.695.403

SHEET 3 0? 3 INVENTOR THOMAS EASTWOOD BY p -LLJ, I NORRIS & BATEMANSYNCHRONIZING MECHANISMS FOR POWER TRANSMISSIONS BACKGROUND OF THEINVENTION The invention relates to synchronizing mechanisms for powertransmissions in which positive clutches are employed to selectivelyconnect torque transmitting members, and more particularly tosynchronizing mechanisms of the type having at least one positiveclutch; a friction clutch associated with the or each positive clutch;one element of the or each friction clutch and one element of theassociated positive clutch each being integral with or rigidly securedto a first torque transmitting member; the other element of saidpositive clutch being formed on a clutching member which is drivablyconnected to and is axially slidable on a second torque transmittingmember; the other element of said friction clutch being carried on aplurality of pins, each pin passing through an offset axial clearancehole in the clutching member; each pin having at least one enlargeddiameter portion forming a shoulder which balks axial movement of theclutching member when the axes of the pins are moved out of alignmentwith the axes of the holes in the clutching member by thecircumferential component of the frictional force created by engagementof the friction clutch elements, and said engagement effectingsynchronization of the speeds of'rotation of the elements of thepositive clutch prior to their engagement.

However, synchronizing mechanisms of the above type suffer from thedisadvantage that wear of the pins and the holes in the clutching membertakes place due to uncontrolled oscillations of the pins within theholes when the friction clutch elements are not engaged. It is alsopossible to slide the clutching member axially on the second torquetransmitting member without corresponding movement of the pins and thuswithout engagement of the friction clutch elements if the pins happen bychance to be centrally aligned in the holes of the clutching member, andas a result synchronization of the speeds of rotation of the elements ofthe positive clutch does not always occur prior to their engagement.

SUMMARY OF THE INVENTION The object of the invention, in its broadestconcept,

is to alleviate the second disadvantage referred to above, and in itspreferred form to alleviate both of the above disadvantages.

According to the invention, in a synchronizing mechanism of the typereferred to each pin is centralised longitudinally within the holes inthe clutching member and urged to move in unison with said member byresilient means.

DESCRIPTION OF THE INVENTION A preferred embodiment of the inventionwill now be described, by way of example only, with reference to theaccompanying drawings of which:

, FIG. 1 is a sectional side elevation of a synchronizing mechanism fora vehicle power transmission;

FIG. 2 is a section on the line 2-2 in FIG. I with parts omitted forclarity;

FIG. 3 is a sectional side elevation of a modified synchronizingmechanism; and

FIG. 4 shows a minor modification of the mechanism of FIG. 3.

Referring now to FIGS. 1 and 2, a vehicle power transmission has a shafton which is rotatably mounted a gear 11 having positive clutch teeth 12formed on it and a friction clutch element 13 rigidly secured to it. Agear 14 having positive clutch teeth 15 formed on it and a frictionclutch element 16 rigidly secured to it is also rotatably mounted on theshaft 10. Two driven members 17 and 18, having external teeth 19 and 20corresponding to the positive clutch teeth 12 and 15 respectively, aresecured to the shaft 10 by means of splines 21. A clutching member 22 isslidable on the teeth 19 and 20 of the members 17 and 18, from acentral, neutral position shown in FIG. 1, to selective ly clutch one ofthe gears 11 and 14 to the shaft 10 by engaging the teeth 12 or theteeth 15. The clutching member 22 has a central portion 23 of enlargeddiameter having an annular groove 24 in its periphery with which aselector fork (not shown), movable axially by means of a gear leveroperated selector rod (not shown), is engagable. Three axial holes 25,whose axes are equally spaced on a common pitch circle, are drilled inthe portion 23 of the member 22, and the ends of each of said holes arechamfered. A pin 26 having enlarged diameter portions 27, 28 passesco-axially through each hole 25. The portion 27 is secured to an annularfriction clutch element 29 and the portion 28 is secured to an annularfriction clutch element 30. The diameter of each hole 25 is such thatthe enlarged portions 27, 28 of its associated pin 26 are a sliding fitin said hole. The ends of the enlarged diameter portions 27, 28 of eachpin 26 adjacent the clutching member 22 are chamfered to form inclinedbalking shoulders 31, 32. The clutching member 22 has two sets of threetransverse milled slots 33. In each slot of one set there is located asingle wire spring 34 and in each slot of the other set there is locateda single wire spring 35. Each of the springs 34, 35 has a centraldepression 36 engaging one of the sloping shoulders 31, 32 of theassociated pin 26, and the ends of each of the springs 34, 35 bearagainst an unmilled portion 37 of the clutching member 22 thus locatingthe associated pin 26 in the center of its hole 25.

In operation, the gears 11 and 14 are constantly driven and the ratio ofthe vehicle power transmission is varied by selectively clutching one ofsaid gears to the shaft 10. When the gear 11 is to be clutched to theshaft 10, the gear lever operated selector rod (not shown) acts throughthe selector fork (not shown) located in the groove 24 to urge theclutching member 22 towards the gear 11. The depression 36 of eachspring 34 bears against the shoulder 31 of the associated pin 26, urgessaid pin to move in unison with the clutching member 22 and thus causesthe friction clutch element 29 to engage the friction clutch element 13secured to the gear 11 before the clutching member 22 connects the teeth12 formed on the gear 11 to the teeth 19 of the driven member 17. Thecircumferential component of the frictional force between the elements29 and 13 moves each pin 26 in a circumferential direction against thecentralising action of the springs 34, 35 so that the shoulder 31 ofeach pin 26 engages that chamfered end of its hold 25 nearest the gear11. Further movement of the clutching member 22 towards the gear 11 isthus prevented until the frictional force between the elements 13 and 29is reduced to such a small value that each pin 26 returns to the centerof its associated hole 25 under the action of the springs 34, 35whereupon each spring 34 is compressed into its slot 33 and theclutching member 22 slides over the enlarged diameter portions 27 of thepins 26 and connects the clutch teeth 12 on the gear 11 to the teeth 19of the driven member 17. This connection is accomplished withoutclashing as the speeds of rotation of the gear 11 and the shaft to whichthe member 17 is secured by the splines 21 are synchronized. In order todisengage the gear 11 from the shaft 10 the clutching member 22 isreturned to its central, neutral position between the gears 11 and 14shown in FIG. 1. Each pin 26 returns to its axially and longitudinallycentralised position within its hole 25 under the action of itsassociated springs 34 and 35 which bear against the sloping shoulders 31and 32 respectively.

When the gear 14 is to be clutched to the shaft 10, the gear leveroperated selector fork (not shown) acts through the selector fork (notshown) located in the groove 24 to urge the clutching member 22 towardsthe gear 14. The depression 36 of each spring 35 bears against theshoulder portion 32 of the associated pin 26, urges said pin to move inunison with the clutching member 22 and causes the friction clutchelement 30 to engage the friction clutch element 16 secured to the gear14 before the clutching member 22 connects the teeth formed on the gear14 to the teeth of the driven member 18. The frictional force betweenthe elements 16 and 30 moves each pin 26 so that the shoulder 32 engagesthat chamfered end of its hole nearest the gear 14, thus preventingfurther movement of the clutching member 22 towards the gear 14 untilthe speeds of rotation of said gear and the shaft 10 are synchronized.When synchronization occurs the clutching member 22 slides over theenlarged diameter portions 28 of the pins 26, compressing each spring 35into its slot 33 and connecting the clutch teeth 15 on the gear 14 tothe teeth 20 of the driven member 18. The gear 14 is thus connected tothe shaft 10 as the driven member 18 is connected to said shaft by thesplines 21.

Referring now to FIGS. 3 and 4, where it is required to connect only asingle gear 11 to the shaft 10, the friction clutch element attached tothat end of each pin 26 remote from the gear 11 is replaced by anannular member 37 secured to each pin 26 and slidable on a reduceddiameter portion 38 of the driven member 17. The springs are replaced bya resilient device comprising one or more Belleville washers, that is tosay plate springs 39 (see FIG. 3) or by a helical compression spring 40(see FIG. 4) located co-axially of the shaft 10 on the portion ofreduced diameter 38 between the annular member 37 and a shoulder 41formed by the portion of reduced diameter 38 on the driving member 17 toprovide the restoring force necessary for returning the pins 26 to theirlongitudinally centralised positions in the holes 25 in the clutchingmember 22.

What I claim is;

1. A synchronizing mechanism having at least one positive clutch; afriction clutch associated with each positive clutch; one element ofeachfriction clutch and one element of its associated positive clutchforming part of a first torque transmitting member; the other element ofsaid positive clutch being formed on a clutching member which isdrivably connected to and is axially slidable on a second torquetransmitting member; the other element of said friction clutch beingcarried on a plurality of pins, each pin passing through a radiallyoffset axial clearance hole in the clutching member; and each pin havingat least one enlarged diameter portion forming a balking shoulder thatcontacts the adjacent edge of its associated clearance hole to preventengagement of the positive clutch if the axes of the pins are notaligned with the axes of the clearance holes, wherein there are providedresilient means engageable with the balking shoulders for urging thepins to move in unison with said clutching member.

2. A synchronizing mechanism according to claim 1, wherein each pin hasonly one balking shoulder and the resilient means comprise a set ofsprings located in transverse slots in the clutching member each ofwhich is engageable with one of the balking shoulders, and wherein thereis provided a resilient device disposed between an annular membersecured to the end of each pin and a shoulder on the second torquetransmitting member.

3. A synchronizing mechanism according to claim 2, wherein saidresilient device is one or more plate springs.

4. A synchronizing mechanism according to claim 2, wherein saidresilient device is a helical compression spring.

5. A synchronizing mechanism according to claim 1, wherein each pin hastwo oppositely inclined balking shoulders and said resilient meanscomprise two sets of springs located in transverse slots in theclutching member, each spring of one set being engageable with one ofthose shoulders inclined in one direction and each spring of the otherset being engageable with one of those shoulders inclined in the otherdirection.

6. A synchronizing mechanism according to claim 2, wherein each springis formed from a single wire and has a central depression engageablewith the balking shoulder of the associated pin.

7. A synchronizing mechanism according to claim 5, wherein each springis formed from a single wire and has a central depression engageablewith the balking shoulder of the associated pin.

8. The synchronizing mechanism defined in claim 1 wherein said resilientmeans comprises spring means mounted on the clutching member, saidspring means acting circumferentially of the clutch to normallycentralize said pins in the respective clearance holes.

1. A synchronizing mechanism having at least one positive clutch; afriction clutch associated with each positive clutch; one element ofeach friction clutch and one element of its associated positive clutchforming part of a first torque transmitting member; the other element ofsaid positive clutch being formed on a clutching member which isdrivably connected to and is axially slidable on a second torquetransmitting member; the other element of said friction clutch beingcarried on a plurality of pins, each pin passing through a radiallyoffset axial clearance hole in the clutching member; and each pin havingat least one enlarged diameter portion forming a balking shoulder thatcontacts the adjacent edge of its associated clearance hole to preventengagement of the positive clutch if the axes of the pins are notaligned with the axes of the clearance holes, wherein there are providedresilient means engageable with the balking shoulders for urging thepins to move in unison with said clutching member.
 2. A synchronizingmechanism according to claim 1, wherein each pin has only one balkingshoulder and the resilient means comprise a set of springs located intransverse slots in the clutching member each of which is engageablewith one of the balKing shoulders, and wherein there is provided aresilient device disposed between an annular member secured to the endof each pin and a shoulder on the second torque transmitting member. 3.A synchronizing mechanism according to claim 2, wherein said resilientdevice is one or more plate springs.
 4. A synchronizing mechanismaccording to claim 2, wherein said resilient device is a helicalcompression spring.
 5. A synchronizing mechanism according to claim 1,wherein each pin has two oppositely inclined balking shoulders and saidresilient means comprise two sets of springs located in transverse slotsin the clutching member, each spring of one set being engageable withone of those shoulders inclined in one direction and each spring of theother set being engageable with one of those shoulders inclined in theother direction.
 6. A synchronizing mechanism according to claim 2,wherein each spring is formed from a single wire and has a centraldepression engageable with the balking shoulder of the associated pin.7. A synchronizing mechanism according to claim 5, wherein each springis formed from a single wire and has a central depression engageablewith the balking shoulder of the associated pin.
 8. The synchronizingmechanism defined in claim 1 wherein said resilient means comprisesspring means mounted on the clutching member, said spring means actingcircumferentially of the clutch to normally centralize said pins in therespective clearance holes.